1. Field of the Invention
This invention relates to a (thio)epoxy compound suitably used in the field of resins such as optical materials including plastic lenses, prisms, optical fibers, information recording media and light emitting diodes which are required to have a high refractive index and a high transparency, as well as resins therefrom.
This invention also relates to a polymerizable composition suitably used as a starting material for a plastic lens for eyeglasses.
2. Description of the Related Art
A plastic lens is lighter and less brittle than an inorganic lens, and dyeable, which has been therefore rapidly prevailing in the areas of optical devices such as a lens of eyeglasses and a camera lens. Such a plastic lens is required to exhibit optical properties including a high refractive index and a high Abbe number and physical properties including high heat resistance and a low specific gravity.
Among these, high heat resistance and a low specific gravity have been considerably achieved by a current plastic lens with a high refractive index. Currently, the resins which may be widely used for these applications, include those prepared by radical polymerization of diethylene glycol bis(allylcarbonate) (referred to as xe2x80x9cD.A.C.xe2x80x9d). These resins have various features such as excellent impact resistance, lightness, excellent dye-affinity, and good processability including machinability and abradability. These resins, however, have a low refractive index (nd) of about 1.50, leading to a lens with thick center and margin. Thus, there is a need for a resin for a lens with a higher refractive index.
Resins with a higher refractive index than D.A.C. resin are known; for example, polythiourethane resins (e.g., JP-A 63-46213); sulfur-containing O-(meth)acrylate resins (e.g., JP-A 1-128966, 3-217412 and 4-16141); and thio(meth)acrylate resins (e.g., JP-A 63-188660 and JP-B 3-59060), in which sulfur atoms are introduced. A polythiourethane resin is well-balanced in its properties, that is, having suitable properties such as a high refractive index and good impact resistance.
A refractive index and an Abbe number are, however, conflicting properties; as the refractive index increases, the Abbe number decreases. It is, therefore, quite difficult to simultaneously improve these properties. Thus, it has been intensively investigated to achieve a high refractive index, preventing an Abbe number from being decreased.
Most typical suggestions of these attempts are processes using a (thio)epoxy compound as described in JP-As 9-110979, 9-71580 and 9-255781.
According to the processes, a high refractive index can be achieved while maintaining a relatively high Abbe number. A resin prepared according to these processes exhibits a refractive index of nd=about 1.70. Thus, it cannot be considered to meet the need for an improved refractive index sufficient to make a margin of an eyeglass significantly thinner while maintaining a high Abbe number, compared with a commercially available common lens with nd=1.67. An thioepoxy resin prepared from an thioepoxy compound tends to turn yellow during heating in a secondary process, long-term storage or its use. Such yellowing may cause tone alteration of an eyeglass which is required to be fashionable. Thus, it may not meet the needs of routine users of eyeglasses. A procedure for solving the problem has been suggested in, e.g., JP-A 10-298287, where athiol compound is added to an thioepoxy compound to prevent yellowing. Although such a process can prevent yellowing, addition of a thiol compound, especially a mono- or bis-functional thiol, may cause significant deterioration of heat resistance, resulting in a lens which cannot give sufficient properties for an application requiring higher heat resistance.
An objective of this invention is to provide a polymerizable composition which can be used to prepare a resin having a very high refractive index and a high transparency, specifically having nd of 1.71 or higher, maintaining a high Abbe number.
Another objective of this invention is to provide a polymerizable composition which can give a resin maintaining a high refractive index and a high heat resistance, and which can prevent yellowing.
The inventors have intensely investigated to solve the above problems and finally have found that a higher refractive index can be provided by using a (thio)epoxy compound having at least one intramolecular disulfide bond which has been believed to be unstable (e.g., Reld. E. E., Organic Chemistry of Bivalent Sulfur Vol.3).
Specifically, one aspect of this invention is a polymerizable composition comprising a (thio)epoxy compound having at least one intramolecular disulfide bond. We have found that the polymerizable composition can be cured to give a resin with a high refractive index of nd=1.71 or higher.
There has been no information for physical properties or other characteristics of a polysulfide polymer prepared by curing a polymerizable composition containing a (thio)epoxy compound comprising at least one intramolecular disulfide bond.
The second aspect of this invention is a polymerizable composition comprising one or more compounds selected from the group of compounds having at least one NH2 group and/or at least one NH group per a molecule as a yellowing inhibitor, having a total molar ratio of 0.001 to 0.5 of NH2 and NH groups in the inhibitor to thioepoxy and epoxy groups in the (thio)epoxy compound comprising at least one intramolecular disulfide bond. We have found that a resin from the second polymerizable composition of this invention exhibits a high refractive index and a high Abbe number without heat resistance reduction or yellowing.
The first aspect of this invention will be described in detail.
A polymerizable composition comprising a (thio)epoxy compound having at least one intramolecular disulfide bond according to the first aspect of this invention contains at least one epoxy or thioepoxy compound having a disulfide bond and an epoxy or thioepoxy group. The composition may contain inorganic and/or organic compounds including polyether or polysulfide oligomers such as dimers, trimers and tetramers thereof, inorganic and organic acids added as a polymerization retarder, solvents or other by-products as long as they are not harmful.
In the specification, the term xe2x80x9c(thio)epoxyxe2x80x9d means thioepoxy or epoxy. Thioepoxy is represented by the following structure: 
A (thio)epoxy compound having at least one intramolecular disulfide bond includes (thio)epoxy compound having one intramolecular disulfide bond such as bis(2,3-epoxypropyl) disulfide and bis(2,3-epithiopropyl) disulfide; (thio)epoxy compounds having two or more intramolecular disulfide bonds such as bis(2,3-epithiopropyldithio)methane, bis(2,3-epithiopropyldithio)ethane, bis(6,7-epithio-3,4-dithiaheptane) sulfide, 1,4-dithian-2,5-bis(2,3-epithiopropyldithiomethyl, 1,3-bis(2,3-epithiopropyldithiomethyl)benzene, 1,6-bis(2,3-epithiopropyldithio)-2-(2,3-epithiopropyldithioethylthio)-4-thiahexane and 1,2,3-tris(2,3-epithiopropyldithio)propane. Among the compounds, (thio) epoxy compounds having one intramolecular disulfide bond represented by formula (1) are preferred. Besides the process described in the document, bis(2,3-epithiopropyl) disulfide can be prepared by reacting bis(2,3-epoxypropyl) disulfide with a sulfurating agent such as a thiocyanate, thiourea, triphenylphosphine sulfide and 3-methylbenzothiazol-2-thione, preferably a thiocyanate and thiourea. 
wherein X and Y are independently oxygen or sulfur and may be different or the same.
A most preferred (thio)epoxy compound having at least one intramolecular disulfide bond is bis(2,3-epithiopropyl) disulfide.
The (thio)epoxy compound having at least one intramolecular disulfide bond may be used to improve a refractive index of a resin prepared by curing a polymerizable composition comprising the (thio)epoxy compound.
A polymerizable composition comprising a (thio)epoxy compound having at least one intramolecular disulfide bond according to the first aspect of this invention may contain resin modifiers for mainly improving resin properties, e.g., adjusting optical properties such as a refractive index; and physical properties such as impact resistance and a specific gravity, as well as handling properties such as the viscosity of the composition.
Resin modifiers which may be used include (thio)epoxy compounds other than those contained in the (thio)epoxy compound having at least one intramolecular disulfide bond according to the first aspect of this invention, thiols, organic mercapto acids, organic acids and acid anhydrides, amino acids, mercaptoamines, amines and olefins including (meth)acrylates.
Specific examples of the thioepoxy compound as a modifier are, but not limited to, linear aliphatic 2,3-epithiopropylthio compounds such as bis(2,3-epithiopropyl) sulfide, bis(2,3-epithiopropyl-thio)methane, 1,2-bis(2,3-epithiopropylthio)ethane, 1,2-bis(2,3-epithiopropylthio)propane, 1,3-bis(2,3-epithiopropylthio)propane, 1,3-bis(2,3-epithiopropylthio)-2-methylpropane, 1,4-bis(2,3-epithiopropylthio)butane, 1,4-bis(2,3-epithiopropylthio)-2-methylbutane, 1,3-bis(2,3-epithiopropylthio)butane, 1,5-bis(2,3-epithiopropylthio)pentane, 1,5-bis(2,3-epithiopropylthio)-2-methylpentane, 1,5-bis(2,3-epithiopropylthio)-3-thiapentane, 1,6-bis(2,3-epithiopropylthio)hexane, 1,6-bis(2,3-epithiopropylthio)-2-methylhexane, 1,8-bis(2,3-epithiopropylthio)-3,6-dithiaoctane, 1,2,3-tris(2,3-epithiopropylthio)propane, 2,2-bis(2,3-epithiopropylthio)-1,3-bis(2,3-epithiopropylthiomethyl)propane, 2,2-bis(2,3-epithiopropylthiomethyl)-1-(2,3-epithiopropylthio)butane, 1,5-bis(2,3-epithiopropyl-thio)-2-(2,3-epithiopropylthiomethyl)-3-thia-pentane, 1,5-bis(2,3-epithiopropylthio)-2,4-bis(2,3-epithiopropylthiomethyl)-3-thiapentane, 1-(2,3-epithiopropylthio)-2,2-bis(2,3-epithio-propylthiomethyl)-4-thiahexane, 1,5,6-tris(2,3-epithiopropylthio)-4-(2,3-epithiopropylthio-methyl)-3-thiahexane, 1,8-bis(2,3-epithiopropyl-thio)-4-(2,3-epithiopropylthiomethyl)-3,6-dithia-octane, 1,8-bis(2,3-epithiopropylthio)-4,5-bis-(2,3-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,8-bis(2,3-epithiopropylthio)-4,4-bis(2,3-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,8-bis-(2,3-epithiopropylthio)-2,5-bis(2,3-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,8-bis(2,3-epithiopropylthio)-2,4,5-tris(2,3-epithiopropyl-thiomethyl)-3,6-dithiaoctane, 1,1,1-tris{[2-(2,3-epithiopropylthio)ethyl]thiomethyl}-2-(2,3-epithiopropylthio)ethane, 1,1,2,2-tetrakis{[2-(2,3-epithiopropylthio)ethyl]thiomethyl}ethane, 1,11-bis(2,3-epithiopropylthio)-4,8-bis(2,3-epithiopropylthiomethyl)-3,6,9-trithiaundecane, 1,11-bis(2,3-epithiopropylthio)-4,7-bis(2,3-epithiopropylthiomethyl)-3,6,9-trithiaundecane and 1,11-bis(2,3-epithiopropylthio)-5,7-bis(2,3-epithiopropylthiomethyl)-3,6,9-trithiaundecane; alicyclic 2,3-epithiopropylthio compounds such as 1,3-bis(2,3-epithiopropylthio)cyclohexane, 1,4-bis(2,3-epithiopropylthio)cyclohexane, 1,3-bis(2,3-epithiopropylthiomethyl)cyclohexane, 1,4-bis(2,3-epithiopropylthiomethyl)cyclohexane, 2,5-bis(2,3-epithiopropylthiomethyl)-1,4-dithiane, 2,5-bis{[2-(2,3-epithiopropylthio)ethyl]-thiomethyl}-1,4-dithiane and 2,5-bis(2,3-epithio-propylthiomethyl)-2,5-dimethyl-1,4-dithiane; aromatic 2,3-epithiopropylthio compounds such as 1,2-bis(2,3-epithiopropylthio)benzene, 1,3-bis-(2,3-epithiopropylthio)benzene, 1,4-bis(2,3-epithiopropylthio)benzene, 1,2-bis(2,3-epithiopropylthiomethyl)benzene, 1,3-bis(2,3-epithiopropylthiomethyl)benzene, 1,4-bis(2,3-epithiopropylthiomethyl)benzene, bis[4-(2,3-epithiopropylthio)phenyl]methane, 2,2-bis[4-(2,3-epithiopropylthio)phenyl]propane, bis[4-(2,3-epithiopropylthio)phenyl] sulfide, bis[4-(2,3-epithiopropylthio)phenyl] sulfone and 4,4xe2x80x2-bis(2,3-epithiopropylthio)biphenyl; monofunctional epithio compounds such as ethylene sulfide and propylene sulfide; and epithio compounds comprising a mercapto group such as 3-mercaptopropylene sulfide and 4-mercaptobutene sulfide.
Specific epoxy compounds which may be used include, but are not limited to, phenolic epoxy compounds prepared by condensation of an epihalohydrin with a polyphenol including bisphenol-A glycidyl ether; alcoholic epoxy compounds prepared by condensation of an epihalohydrin with a polyalcohol including hydrogenated bisphenol-A glycidyl ether; glycidyl ester epoxy compounds prepared by condensation of an epihalohydrin with an organic polyacid derivative including 3,4-epoxycyclohexylmethyl-3xe2x80x2,4xe2x80x2-epoxycyclohexane carboxylate and diglycidyl 1,2-hexahydrophthalate; amino epoxy compounds prepared by condensation of an epihalohydrin with a secondary amine; and aliphatic polyepoxy compounds such as vinylcyclohexene diepoxide.
Specific thiols which may be used include, but are not limited to, aliphatic thiols such as methyl mercaptan, ethyl mercaptan, 1,2-ethanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 2,2-propanedithiol, 1,4-butanedithiol, 1,2,3-trimercaptopropane, tetrakis(mercaptomethyl)-methane, 1,2-dimercaptocyclohexane, bis(2-mercaptoethyl) sulfide, 2,3-dimercapto-1-propanol, ethyleneglycol bis(3-mercaptopropionate), diethyleneglycol bis(3-mercaptopropionate), diethyleneglycol bis(2-mercaptoglycolate), pentaerythritol tetrakis(2-mercaptothioglycolate), pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane tris(2-mercaptothioglycolate), trimethylolpropane tris(3-mercaptopropionate), 1,1,1-trimethylmercaptoethane, 1,1,1-trimethylmercaptopropane, 2,5-dimercaptomethylthiophane, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 2,5-dimercaptomethyl-1,4-dithiane, 2,5-bis[(2-mercaptoethyl)thiomethyl]-1,4-dithiane, 1,3-cyclohexanedithiol, 1,4-cyclohexanedithiol, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane and 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane; and aromatic thiols such as benzylthiol, thiophenol, 1,2-dimercaptobenzene, 1,3-dimercaptobenzene, 1,4-dimercaptobenzene, 1,2-bis(mercaptomethyl)-benzene, 1,3-bis(mercaptomethyl)benzene, 1,4-bis(mercaptomethyl)benzene, 2,2xe2x80x2-dimercaptobiphenyl, 4,4xe2x80x2-dimercaptobiphenyl, bis(4-mercaptophenyl)methane, bis(4-mercaptophenyl) sulfide, bis(4-mercaptophenyl) sulfone, 2,2-bis(4-mercaptophenyl)propane, 1,2,3-trimercaptobenzene, 1,2,4-trimercaptobenzene and 1,2,5-trimercaptobenzene.
Organic mercapto acids which may be used include, but are not limited to, thioglycolic acid, 3-mercaptopropionic acid, thioacetic acid, thiolactic acid, thiomalic acid and thiosalicylic acid. Organic acids and their anhydrides which may be used include, but are not limited to, the above polymerization retarders as well as thiodiglycolic acid, thiodipropionic acid, dithiodipropionic acid, phthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnorbornenoic anhydride, methylnorbornanoic anhydride, maleic anhydride, trimellitic anhydride and pyromellitic dianhydride.
Olefins which may be used include, but are not limited to, (meth)acrylates such as benzyl acrylate, benzyl methacrylate, butoxyethyl acrylate, butoxymethyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenyl methacrylate, 3-phenoxy-2-hydroxypropyl acrylate, ethyleneglycol diacrylate, ethyleneglycol dimethacrylate, diethyleneglycol diacrylate, diethyleneglycol dimethacrylate, triethyleneglycol diacrylate, triethyleneglycol dimethacrylate, tetraethyleneglycol diacrylate, tetraethyleneglycol dimethacrylate, polyethyleneglycol diacrylate, polyethyleneglycol dimethacrylate, neopentylglycol diacrylate, neopentylglycol dimethacrylate, ethyleneglycolbisglycidyl diacrylate, ethyleneglycolbisglycidyl dimethacrylate, bisphenol-A diacrylate, bisphenol-A dimethacrylate, 2,2-bis(4-acryloxyethoxyphenyl)propane, 2,2-bis(4-methacryloxyethoxyphenyl)propane, 2,2-bis(4-acryloxydiethoxyphenyl)propane, 2,2-bis(4-methacryloxydiethoxyphenyl)propane, bisphenol-F diacrylate, bisphenol-F dimethacrylate, 1,1-bis(4-acryloxyethoxyphenyl)methane, 1,1-bis(4-methacryloxyethoxyphenyl)methane, 1,1-bis(4-acryloxydiethoxyphenyl)methane, 1,1-bis(4-methacryloxydiethoxyphenyl)methane, dimethyloltricyclodecane diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol diacrylate, glycerol dimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, methylthio acrylate, methylthio methacrylate, phenylthio acrylate, benzylthio methacrylate, xylenedithiol diacrylate, xylenedithiol dimethacrylate, mercaptoethylsulfide diacrylate and mercaptoethylsulfide dimethacrylate; allyl compounds such as allyl glycidyl ether, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diallyl carbonate and diethyleneglycol-bisallyl carbonate; vinyl compounds such as styrene, chlorostyrene, methylstyrene, bromostyrene, dibromostyrene, divinylbenzene and 3,9-divinyl-spiro-bis(m-dioxane); and diisopropenylbenzene.
These resin modifiers may be used alone or in combination of two or more thereof.
Curing catalysts which may be used in the first aspect of this invention may be typically tertiary amines, phosphines, Lewis acids, radical polymerization catalysts and cationic polymerization catalysts.
The preferable curing catalysts include, but are not limited to, aliphatic and aromatic tertiary amines such as triethylamine, tri-n-butylamine, tri-n-hexylamine, N,N-diisopropylethylamine, triethylenediamine, triphenylamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dibutylethanolamine, triethanolamine, N-ethyldiethanolamine, N,N-dimethylbenzylamine, N,N-diethylbenzylamine, tribenzylamine, N-methyldibenzylamine, N,N-dimethylcyclohexylamine, N,N-diethylcyclohexylamine,N,N-dimethylbutylamine, N-methyldicyclohexylamine, N-methylmorpholine, N-isopropylmorpholine, pyridine, quinoline, N,N-dimethylaniline, N,N-diethylaniline, xcex1, xcex2- or xcex3-picoline, ,2xe2x80x2-dipyridyl, 1,4-dimethylpiperazine, dicyandiamide, tetramethylethylenediamine, hexamethylenetetramine, 1,8-diazabicyclo[5.4.0]-7-undecene and 2,4,6-tris(N,N-dimethylaminomethyl)phenol; phosphines such as trimethylphosphine, triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tribenzylphosphine, 1,2-bis(diphenylphosphino)ethane and 1,2-bis(dimethylphosphino)ethane; Lewis acids such as dimethyltin dichloride, dibutyltin dichloride, dibutyltin dilaurate, tetrachlorotin, dibutyltin oxide, zinc chloride, zinc acetylacetonate, aluminum chloride, aluminum fluoride, triphenylaluminum, titanium tetrachloride and calcium acetate; radical polymerization catalysts such as 2,2xe2x80x2-azobis(2-cyclopropylpropionitrile), 2,2xe2x80x2-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2xe2x80x2-azobis(2,4-dimethylvaleronitrile), t-butylperoxy-2-ethyl hexanoate, n-butyl-4,4xe2x80x2-bis(t-butylperoxy)valerate and t-butyl peroxybenzoate; and cationic polymerization catalysts such as diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, diphenyliodonium hexafluoroantimony, triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluorophosphate and triphenylsulfonium hexafluoroarsenate.
These curing catalysts may be used alone or in combination of two or more thereof.
A curing catalyst may be preferably added in a proportion of 0.001 to 10 wt %, more preferably 0.01 to 5 wt % to the total amount of the polymerizable composition comprising a (thio)epoxy compound. If the proportion is less than 0.001 wt %, polymerization may be insufficient due to a too small effect of the catalyst. On the other hand, the catalyst may be contained in a proportion of more than 10 wt %, but it may cause problems such as a shorter pot life and deterioration in transparency, optical properties or weatherproof properties.
A typical polymerization process for preparing the resin according to the first aspect of this invention (e.g., a plastic lens) is casting polymerization. Specifically, a polymerizable composition comprising a (thio)epoxy compound and a curing catalyst, which may be also referred to as a monomer mixture, is poured between molds held by a fixing means such as a gasket and tapes, during which some treatments such as defoaming may be, if necessary, conducted.
Then, it may be subject to curing by heating in a heating apparatus such as an oven or in water, and then a polymerization product may be removed from the mold.
A polymerization method or polymerization conditions for preparing a resin according to the first aspect of this invention cannot be generalized since they depend on the amounts and types of ingredients such as curing catalysts as well as types and proportions of monomers.
Heat curing conditions in the mold for a polymerizable composition according the first aspect of this invention significantly vary depending on various factors such as a type of a composition comprising a (thio)epoxy compound, a type of a curing catalyst and the shape of the mold and therefore cannot be specifically limited, but the composition may be typically cured at xe2x88x9250 to 200xc2x0 C. for 1 to 100 hours. It may be cured keeping or gradually raising the temperature within a range of 10xc2x0 C. to 150xc2x0 C. for 1 to 80 hours, providing good results.
In addition, a composition comprising a (thio)epoxy compound having at least one intramolecular disulfide bond, especially a (thio)epoxy compound having an intramolecular disulfide bond, may be cured in a reduced time by UV irradiation, where a curing catalyst such as a radical polymerization catalyst may be necessary.
For molding a resin according to the first aspect of this invention, a variety of substances such as chain extenders, crosslinking agents, photostabilizers, UV absorbents, antioxidants, anti-coloring agents, dyes, fillers and internal mold release agents, may be added, depending on the purpose, as in the known molding methods.
The resin, which has been removed from the mold, may be, if necessary, annealed.
A resin obtained by curing a polymerizable composition comprising a (thio)epoxy compound having at least one intramolecular disulfide bond according to the first aspect of this invention has a high refractive index, a reduced dispersibility and a high thermal resistance, especially an extremely high refractive index. It is a transparent resin having a refractive index of preferably ndxe2x89xa71.71, more preferably ndxe2x89xa71.72, most preferably ndxe2x89xa71.73. Furthermore, the resin of this invention can be formed in various forms by altering a mold in the casting polymerization, and be thus used as optical device materials for an eyeglass lens, a camera lens and a light emitting diode (LED), as well as a transparent resin for a variety of applications. In particular, it is suitable for an optical device material for an eyeglass lens and a camera lens.
Furthermore, a lens from the resin according to the first aspect of this invention may be, if necessary, subject to physical or chemical post-treatments such as surface abrasion, antistatic treatment, hard coating, non-reflection coating and dyeing, for improvements such as prevention of reflection; improvement in hardness, abrasion resistance or chemical resistance; and impartation of antifog or cosmetic property.
Next, the second aspect of this invention will be described in detail.
JP-As 9-110979, 9-71580, 9-255781 and 10-298287 describing thioepoxy resins list primary and secondary amines corresponding to Compound (b) according to the second aspect of this invention as a curing catalyst, but they have disclosed only hydrogenated 4,4xe2x80x2-diaminodiphenylmethane in their examples and comparative examples. In our investigation, when hydrogenated 4,4xe2x80x2-diaminodiphenylmethane was used as a curing catalyst, a reaction mixture became cloudy and lost transparency due to local polymerization immediately after adding 4,4xe2x80x2-diaminodiphenylmethane to an thioepoxy compound. In addition, polymerization could not be completed even after heating and thus a satisfactory resin was not obtained. Among the other amines listed except tertiary amines, primary and secondary amines corresponding to a compound having an amino group and/or an imino group of this invention did not exhibit satisfactory effects as a curing catalyst, so that the polymerization was not completed and a viscous liquid or a gummy resin was provided. Thus, we have found that primary and secondary amines can be used not as a curing catalyst for an thioepoxy resin, but as an yellowing inhibitor which may prevent deterioration in heat resistance.
In the second aspect of this invention, the composition has a proportion of 0.001 to 0.5, preferably equal to or more 0.01 and less than 0.3 of the total molar number of NH2 and NH groups in the above primary and secondary amines (referred to as Compound (b)) to the total molar number of thioepoxy and epoxy groups in a (thio)epoxy compound having at least one intramolecular disulfide bond (referred to as Compound (a)).
If the total molar ratio is more than 0.5, a resulting resin after polymerization has reduced heat resistance and a lower refractive index. If the ratio is less than. 0.001, yellowing cannot be adequately prevented as intended in the second aspect of this invention.
A polymerizable composition according to the second aspect of this invention comprises Compounds (a) and (b), and may contain inorganic and/or organic compounds including polyether or polysulfide oligomers such as dimers, trimers and tetramers thereof, inorganic and organic acids added as a polymerization retarder, solvents or other by-products as long as they are not harmful.
A polymerizable composition according to the second aspect of this invention may contain resin modifiers for mainly improving resin properties, e.g., adjusting optical properties such as a refractive index; and physical properties such as impact resistance and a specific gravity, as well as improving handling properties as the viscosity of the composition.
Resin modifiers which may be used are as described above.
Preferable examples of Compound (b) in the second aspect of this invention are, but not limited to,
(1) monofunctional primary amines such as ethylamine, n-propylamine, isopropylamine, n-butylamine, sec-butylamine, tert-butylamine, pentylamine, hexylamine, heptylamine, octylamine, decylamine, laurylamine, myristylamine, 3-pentylamine, 2-ethylhexylamine, 1,2-dimethylhexylamine, allylamine, aminomethylbicycloheptane, cyclopentylamine, cyclohexylamine, 2,3-dimethylcyclohexylamine, aminomethylcyclohexane, aniline, benzylamine, phenethylamine, 2-, 3- or 4-methylbenzylamine, o-, m- or p-methylaniline, o-, m- or p-ethylaniline, aminomorpholine, naphthylamine, furfurylamine, a-aminodiphenylmethane, toluidine, aminopyridine, aminophenol, aminoethanol, 1-aminopropanol, 2-aminopropanol, aminobutanol, aminopentanol, aminohexanol, methoxyethylamine, 2-(2-aminoethoxy)ethanol, 3-ethoxypropylamine, 3-propoxypropylamine, 3-butoxypropylamine, 3-isopropoxypropylamine, 3-isobutoxypropylamine and 2,2-diethoxyethylamine; and primary polyamines such as ethylenediamine, 1,2-or 1,3-diaminopropane, 1,2-, 1,3- or 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,10-diaminodecane, 1,2-, 1,3- or 1,4-diaminocyclohexane, o-, m- or p-diaminobenzene, 3,4- or 4,4xe2x80x2-diaminobenzophenone, 3,4- or 4,4xe2x80x2-diaminodiphenyl ether, 4,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenyl sulfide, 3,3xe2x80x2- or 4,4xe2x80x2-diaminodiphenyl sulfone, 2,7-diaminofluorene, 1,5-, 1,8- or 2,3-diaminonaphthalene, 2,3-, 2,6- or 3,4-diaminopyridine, 2,4- or 2,6-diaminotoluene, m- or p-xylylenediamine, isophoronediamine, diaminomethylbicycloheptane, 1,3- or 1,4-diaminomethylcyclohexane, 2- or 4-aminopiperidine, 2- or 4-aminomethylpiperidine, 2- or 4-aminoethylpiperidine, N-aminoethylmorpholine and N-aminopropylmorpholine;
(2) monofunctional secondary amines such as diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, diisobutylamine, di-n-pentylamine, di-3-pentylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, methylhexylamine, diallylamine, N-methylallylamine, piperidine, pyrrolidine, diphenylamine, N-methylphenylamine, N-ethylphenylamine, dibenzylamine, N-methylbenzylamine, N-ethylbenzylamine, dicyclohexylamine, N-methylaniline, N-ethylaniline, dinaphthylamine, 1-methylpiperazine and morpholine; and secondary polyamines such as N,Nxe2x80x2-dimethylethylenediamine, N,Nxe2x80x2-dimethyl-1,2-diaminopropane, N,Nxe2x80x2-dimethyl-1,3-diaminopropane, N,Nxe2x80x2-dimethyl-1,2-diaminobutane, N,Nxe2x80x2-dimethyl-1,3-diaminobutane, N,Nxe2x80x2-dimethyl-1,4-diaminobutane, N,Nxe2x80x2-dimethyl-1,5-diaminopentane, N,Nxe2x80x2-dimethyl-1,6-diaminohexane, N,Nxe2x80x2-dimethyl-1,7-diaminoheptane, N,Nxe2x80x2-diethylethylenediamine, N,Nxe2x80x2-diethyl-1,2-diaminopropane, N,Nxe2x80x2-diethyl-1,3-diaminopropane, N,Nxe2x80x2-diethyl-1,2-diaminobutane, N,Nxe2x80x2-diethyl-1,3-diaminobutane, N,Nxe2x80x2-diethyl-1,4-diaminobutane, N,Nxe2x80x2-diethyl-1,5-diaminopentane, N,Nxe2x80x2-diethyl-1,6-diaminohexane, N,Nxe2x80x2-diethyl-1,7-diaminoheptane, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, homopiperazine, 1,1-di-(4-piperidyl)methane, 1,2-di-(4-piperidyl)ethane, 1,3-di-(4-piperidyl)propane, 1,4-di-(4-piperidyl)butane and tetramethylguanidine. These may be used alone or in combination of two or more thereof. More preferable compounds are benzylamine and piperazines.
A polymerizable composition according to the second aspect of this invention may be cured by heating or being left at an ambient temperature in the presence or absence of a curing catalyst, to provide a resin. It may be preferable to use a curing catalyst since curing may not proceed adequately or at all in the absence of the catalyst. Typical curing catalysts which may be used for the second aspect of this invention include amines other than Compound (b) in the second aspect of this invention, phosphines, Lewis acids, radical polymerization catalysts and cation polymerization catalysts as described in terms of the first aspect of this invention.
A curing catalyst may be preferably added in a proportion of 0.001 to 10 wt %, more preferably 0.01 to 1 wt % to the total amount of the polymerizable composition comprising Compound (a) having an epoxy or thioepoxy group. If its proportion is less than 0.001 wt %, polymerization may be insufficient due to a too small effect of the catalyst. On the other hand, the catalyst may be contained in a proportion of more than 10 wt %, but it may cause problems such as a shorter pot life and deterioration in transparency, optical properties or weatherproof properties.
A typical polymerization process for preparing the resin according to the second aspect of this invention(e.g., a plastic lens) is casting polymerization. Specifically, a polymerizable composition according to the second aspect of this invention, after mixing, if necessary, with a curing catalyst and/or a resin modifier, is poured between molds held by a fixing means such as a gasket and tapes. Before or after pouring, some treatments such as defoaming may be, if necessary, conducted.
Then, it may be subject to curing by heating in a heating apparatus such as an oven or in water, and then a polymerization product may be removed from the mold.
A polymerization method and polymerization conditions for preparing a resin according to the second aspect of this invention cannot be generalized since they depend on the amounts and types of ingredients such as curing catalysts as well as types and proportions of monomers.
Heat curing conditions for a polymerizable composition according the second aspect of this invention poured into the mold significantly vary depending on various factors such as Compounds (a) and (b) in the second aspect of this invention, a type of a resin modifier, a type of a curing catalyst and the shape of the mold and therefore cannot be specifically limited, but the composition may be typically cured at xe2x88x9250 to 200xc2x0 C. for 1 to 100 hours.
It may be cured keeping or gradually raising the temperature within a range of 10xc2x0 C. to 150xc2x0 C. for 1 to 80 hours, providing good results.
In addition, the polymerizable composition according to the second aspect of this invention may be cured in a reduced time by UV irradiation, where a curing catalyst such as a radical polymerization catalyst may be added.
For molding a resin according to the second aspect of this invention, a variety of substances such as chain extenders, crosslinking agents, photostabilizers, UV absorbents, antioxidants, anti-coloring agents other than those in the second aspect of this invention, dyes, fillers, internal and external mold release agents, internal and external adherence improver and compounds having a hydroxy group as a dye-affinity improver may be added, depending on the purpose, as in the known molding methods.
The resin, which has been removed from the mold, may be, if necessary, annealed. Furthermore, the resin of the second aspect of this invention can be formed in various forms by altering a mold in the casting polymerization, and be thus used as an optical material for an eyeglass lens, a camera lens and a light emitting diode (LED), as well as a transparent resin for a variety of applications. In particular, it is suitable for an optical material for an eyeglass lens and a camera lens.
Furthermore, a lens from the optical material according to the second aspect of this invention may be, if necessary, subject to physical or chemical post-treatments such as surface abrasion, antistatic treatment, hard coating, non-reflection coating and dyeing, for improvements such as prevention of reflection; improvement in hardness, abrasion resistance or chemical resistance; and impartation of antifog or cosmetic property.